It looks like some writers in this thread think the output of speaker-cabinets depends on the impedance (Z) of the speakers ?!

The lower the Z, the higher the audio-power.... but be careful please !!

The optimum match between an amp and speaker is when they both have the same impedance. Current amps are able to auto-adjust within limits, but there ARE limits. (max.speaker Z and min.speaker Z)
When users keep lowering the speaker impedance often amps get damaged because the power-supplies and other components get overheated.

There are 400W speakers with 4 Ohm Z, but also 400W speakers with 8 Ohms. The amp used for the 2nd one has the double output voltage.

Roel